1. Field of the Invention
The present invention relates to a multi-cylinder engine in which a plurality of combustion chambers are formed between a cylinder head fastened to a cylinder block including a plurality of cylinder bores and pistons slidably fitted in the plurality of cylinder bores. A cam shaft linked with a plurality of intake valves and a plurality of exhaust valves for carrying out intake and exhaust operations for the combustion chambers is rotatably supported at a plurality of locations spaced in the axial line direction of said cam shaft by cam bearing portions provided on the cylinder head and a cam holder fastened to the cam bearing portions. Furthermore, an oil passage capable of supplying oil from an oiling passage provided in the cylinder head is formed in the cam shaft. In particular, the present invention relates to a structure for supplying oil from a cylinder head into an oil passage formed in a cam shaft.
2. Description of Related Art
In a conventional multi-cylinder engine, an oil groove for supplying oil into an oil passage in a cam shaft is generally provided in a can bearing portion for supporting one end portion of the cam shaft in the axial direction. The cam bearing portion is disposed outside of the outermost one of a plurality of combustion chambers disposed in the axial line direction of the cam shaft.
A cylinder head is fastened to a cylinder block using fastening bolts disposed at a plurality of locations other than portions corresponding to a plurality of combustion chambers. To shorten the length of the cylinder head in the axial line direction of a cam shaft, it may be desirable to make the fastening bolt disposed outside the outermost combustion chamber as close to the outermost combustion chamber as possible. If the fastening bolt can be disposed in a portion corresponding to a cam bearing portion outside the outermost combustion chamber, the length of the cylinder head can be shortened. However, since an oil groove is generally provided in the above cam bearing portion disposed outside the outermost combustion chamber as described above, it is difficult to dispose the fastening bolt in the portion corresponding to the above cam bearing portion without interference with the oil groove